Fluid metering system



Feb. 8, 1966 J. E. SMITH FLUID METERING SYSTEM 5 Sheets-Sheet l FiledMay 28 1962 N (1J J M ML RH d ff N of @M T/ N as v/J 0 /P N f E d l R MfC f pw@ .n H A P N /f/ mr H Hw 0 0 C Ml d /fv Y fw B cf n MM www 0057'PUMP Feb. 8, 1966 J. E. SMITH 3,233,65

FLUID METERING SYSTEM Filed May 28 1962 5 Sheets-Sheet 2 /0 7:' y 3awp/fijar@ my ,o/efssmf BY 77 if 46 4J ,f ,f f f,

Feb. 8, 1966 J. E, SMITH 3,233,551

FLUID METERING SYSTEM Filed May 28, 1962 5 Sheets-Sheet 5 United StatesPatent O 3,233,651 FLUIB METERING SYSTEM John E. Smith, Rochester,Mich., assigner to Holley Carburetor Company, Warren, Mich., acorporation of Michigan Filed May 28, 1962, Ser. No. 198,175 7 Claims.(Cl. 158-4163) The invention relates to a uid metering system and refersmore specifically to a-pparatus for metering fuel at low pressure to ahigh pressure positive displacement fuel pump without throttling thepump input `and supplying only the metered fuel at high pressure fromthe output of the high pressure pump to a utilizing device.

In the past fuel metering systems for turbine engines and the like havegenerally utilized high pressure fuel metering and have been of thecontrolled pump, spill flow or high pressure flow met-er types. Each ofthese metering systems has disadvantages. The high pressure flow metersare complicated and expensive while the variable displacement controlledpumps are often inaccurate at other than low speeds and minimum backpressure. The spill flow metering systems wherein a portion of the highpressure fuel is recirculated is generally subject to both theobjections of high cost and inaccuracies in that some sort yof variabledisplacement or otherwise controlled pump is usually included therein.

Prior low pressure fuel metering systems have usually been of the pumpthrottling or starving type wherein a positive displacement highpressure pump has been fed variable amounts of low pressure fuel. Suchsystems have the distinct disadvantage in that due to the variablevolume of fuel fed the positive displacement pump bubbles are entrainedin the fuel which on collapsing within the pump rapidly erode the pumpsurfaces.

It is therefore one of the objects of the invention to provide animproved fluid metering system including a positive displacement highpressure pump fed by a low pressure uid metering control.

Another object is to provide a fuel metering system including a positivedisplacement high pressure pump, fed by a low pressure fuel meteringcontrol which system does not require throttling of the pump input.

Another object is to provide a fuel metering system including means fordelivering fuel at a relatively low pressure to a low pressure fuelcontrol operable to meter the fuel t-o a positive displacement highpressure pump in accordance with the requirements of a utilizing deviceand means for returning a variable portion of the fuel pumped by thehigh pressure pump from the pump output to the pump input in accordancewith the requirements of the fuel utilizing device whereby the fueldelivered to the utilizing device is identical to that delivered to thehigh pressure pump by the low pressure fuel control and a volume of fuelow through the high pressure pumpl which is constant for each pump speedis maintained.

Anotherfobject is to provide a fuel metering system as set forth abovewherein the means for returning a portion of the pumped fuel around thehigh pressure pump comprises a conduit between the input and output ofthe high pressure pump including a restricting valve therein responsiveto the variations in pressure at the pumpl inlet caused by the variablelow pressure fuel delivery to the high pressure pump from the fuelmetering control.

Another object is to provide a fuel metering system as set forth abovewherein the restricting valve is responsive to the pressure differencebetween the fuel fed to the input of a low pressure pump feeding fuel tothe low pressure fuel metering control and the output of the lowpressure fuel metering control.

Another object is to provide a fuel metering system as set forth abovewherein the restricting valve is responsive to the fuel pressuredifference across an ele'- ment of the low pressure fuel meteringcontrol.

Another object is to provide a fuel metering system as set forth abovewherein a boo-st pump is: provided between a fuel reservoir and a lowpressure pump feeding fuel to the low pressure fuel metering control.

Another object is to provide a fuel metering system as set forth abovewherein a tank transferl pump is provided between the fuel tank and theboost pump.

Another object is to prov-ide a fuel metering system as set forth abovewherein the restricting valve comprises a housing, a spring biaseddiaphragm in` the housing carrying a valve member therewith, a firstchamber formed by the housing and diaphragm and a second chamber formedby the diaphragm and housing which second chamber is in communicationwith a third chamber through an opening regulated by said valve member.

Another object is to provide a fuel metering system as set forth abovewherein the biasing spring is in the first chamber and urges the valvetoward the open` position.

Another object is to provide a fuel metering system as set forth abovewherein the valve spring is in the second chamber and urges the valveinto a closed position.

Another lobject is to provide a fluid metering valve including ahousing, a diaphragm supported. by said housing defining with saidhousing a pair of chambers, means biasing the diaphragm toward one ofsaid chambers, a

low pressure conduit communicating with said one chamber, a third,fourth and fth chamber defined by said housing, a low pressure conduitin communication with the first, third and fifth chambers, a valvemember oph eratively connected to the diaphragm and extending betweenthe second and third chambers in engagement with a valve pusherextending through the fourth chamber and between the third and iifthchambers operable to regulate a valve opening between the third landfourth chambers, means biasing said valve member toward the thirdchamber into a closing relation to said val-ve opening and a highpressure conduit for feeding high pressure uid into the fourth chamber.

Another object is to provide a fuel metering system which is simple inconstruction, economical to manufacture and efficient in use.

Other objects and features of the invention will become apparent as thedescription proceeds, especially when taken in conjunction with theaccompanying drawings, illustrating preferred embodiments of 'theinvention, wherein:

FIGURE 1 is a diagrammatic representation of a fuel metering systemconstructed in accordance with the invention.

FIGURES 2-5 illustrate modifications of the fuel metering system shownin FIGURE 1.

FIGURE 6 is a diagrammatic section view of a modification of therestricting valve of the fuel metering systems illustrated in FIGURESl-S.

FIGURE 7 is a graph illustrating the pressure in the outlet conduit fromthe high pressure pump of a fuel metering system such as illustrated inFIGURE 1 plotted against nozzle fuel flow illustrating a characteristicnozzle fuel flow with the fuel metering system of FIGURE l attached to apredetermined engine.

With particular reference to the gures, one embodiment of the presentinvention will now be disclosed.

The fuel metering system 10 illustrated in FIGURE 1 includes a fuel tankl2 connected to a fuel control package 14 including a low pressure pump16 and a low pressure fuel metering control 18. A high pressure 'nozzleand burner for a jet engine.

pump connected to the metering control 18 and a pressure sensitive valve22 connected between the fluid tank 12 and pump 16, between the meteringcontrol 18 and high pressure pump 2t) and between the high pressure pump20 and a utilizing device, such as a nozzle 24 and burner 26, completethe fuel metering system 10.

In operation fuel is pumped to the metering control 18 from the fueltank 12 by the low pressure pump 16 and is metered in accordance withthe requirements of the burner 26 to the nozzle 24 through the highpressure pump 2t). The high pressure pump 28 is a positive displacementpump operable to increase the pressure of the fuel fed thereto from themetering control 18. The pressure sensing valve 22 is operable inresponse to a change in pressure between the output of the meteringcontrol 18 and the input to the low pressure pump to vary the portion ofthe volume of fuel pumped by the high pressure pump 20 which is fed backto the input side of the high pressure pump 28 so that the mass rate offuel flow delivered by the metering control 18 and that delivered to thenozzle 24 is identical. The pressure between the output of the meteringcontrol 18 and the input to the low pressure pump may vary while boththe low pressure and high pressure pumps are at constant speed due tovarying engine fuel requirements sensed by the metering control 18 whichrequire variable quantities of fuel to be metered from the control 18.Obviously this pressure may also vary when the speed of the highpressure pump Vis varied.

More specifically the fuel tank 12 may be for example a fuel tank of anaircraft which may be maintained at substantially atmospheric pressure.The fuel tank as show in FIGURE 1 is connected to the fuel controlpackage 14 by means of the fuel transfer conduit 28 extending betweenthe fuel tank and fuel control package 14.

The fuel control package 14, as previously indicated, includes a lowpressure pump 16 and the low pressure fuel metering control 18. As setforth above the Huid metering control 18 may be constructed simpler andmore accurate than a high pressure fuel metering control for meteringthe same quantity of fuel due to the low pressure at which it operates.Since low pressure fuel metering controls in combination with lowpressure pumps such as 16 are well known in the fuel metering arts inthe interest of simplicity the details of construction thereof are notshown.

Similarly high pressure positive displacement pumps such as pump 20 arewell known in the pumping art and are much simpler, more accuratelycontrollable and more eicient in operation than presently known variabledisplacement high pressure pumps. The high pressure pump 20 willtherefore not be disclosed in detail. As previously indicated the highpressure pump 2t) is connected to the metering control 18 by means ofthe intermediate conduit 30.

The nozzle 24 and burner 26 may be for example a The nozzle 24 isconnected to the high pressure pump 20 through the discharge conduit 32.

Pressure sensitive valve 22 comprises a housing including parts 34 and36 constructed as shown best in FIGURE l to provide a chamber 38 and achamber 40 in conjunction with the diaphragm 42 secured therebetween.The housing part 36 includes a guide passage 46 in which a valve member48 secured to diaphragm 42 for movement therewith is reciprocal tocontrol the opening of the valve orifice 44. The valve orifice 44permits more or less communication between the chamber 40 and a separatechamber 50 provided in the housing part 36, as shown in FIGURE l.Another chamber 52 is provided in the valve part 36 in communicationwith chamber 40 to receive the end of valve member 48 as shown inFIGURES 1-5 and assist in balancing the pressures acting on the valvemember 48.

Thus the valve member 48 is responsive primarily to pressure changebetween the fuel in chamber 38 and that in chamber 40 to permit more orless fuel from chamber to flow into chamber 40. Therefore since thechamber 5i) is connected to the high pressure output side of the pump 20through fuel return conduit 54 and since the chamber 40 is connected tothe intermediate conduit 30 through the fuel return conduit 56 it Willbe seen that the quantity of fuel pumped by the high pressure pump 20which is received at the nozzle 24 will vary with the position of thediaphragm 42 with a constant volume of fuel pumped by the high pressurepump 20. The position of the diaphragm 42 will depend on therelativepressures in the chambers 38 and 40 as determined by the pressure in thefuel transfer conduit 28 and the pressure in the intermediate conduit30.

Thus in over-all operation with the fuel metering system shown in FIGURE1 in equilibrium so that a predetermined volume of the fuel pumped bythe high pressure pump 20 at each predetermined pump speed is being fedto the nozzle 24 and the rest of the fuel pumped by the high pressurepump 20 is being returned to the input side of the pump 2t) through thevalve 22, if the burner 26 requires more fuel which requirement isregistered on the fuel metering control 18 in the usual manner, morefuel is metered through the fluid metering control 18 into conduit 30.The pressure of the fuel in conduit 30 is thereby increased so thatdiaphragm 42 is caused to move upward in FIGURE 1 in opposition to thebias applied to the diaphragm 42 by the bias spring 68. Upward movementof the diaphragm 42 causes a restriction of the orifice 44 by the valvemember 48 so that the portion of constant volume of fuel pumped by thepump 20 which is returned to the input side of the pump is reduced andthe required additional fuel is pumped to the nozzle 24.

If the fuel requirement of the burner is lowered the opposite actiontakes place whereby the pressure in chainber 4t) is lowered and valvemember 48 is opened so that more of `the fuel pumped by the highpressure pump 20 is returned `through orifice 44 to the input side ofthe high pressure pump 20 and less is available at the nozzle 24.

Thus it will be seen that a simple, economical and eficient fuelmetering system has been provided in which a high pressure positivedisplacement pump is fed by a l-ower pressure fuel meter-ing control.Further it will be readily recognized that the positive displacementpump 20 is not subject to the rapid deterioration which is present inhigh pressure pumps wherein the output is controlled by input throttlingor starving and that the fuel fed to the pump 20 will be identical inquantity with the fuel metered by the fuel metering control 18 inaccordance with the requirements of the burner 26.

In the several modifications of the fuel metering system shown inFIGURES 2 through 5 the same reference characters have Ibeen used todenote the same or similar elements. New reference characters have beenused to designate additional elements in FIGURES 2 through 5 and in themodified valve illustrated in FIGURE 6.

The modification of the invention illustrated in FIG- URE 2 includes aboost pump 62 placed in the transfer conduit Z8 between the fuel tank 12and low pressure pump 16. Also, in FIGURE 2 it will be noted that theconduit 58 and the return conduit S6 are indicated as being connectedacross an element of the fuel metering control which element providesthe required pressure difference variable in accordance with the fuelrequirements of the burner 26.

It will be readily recognized by those in the art that with most knownlow pressure uid metering controls a number of pressures variable inaccordance with the requirements of a utilizing device are present inthe controls. Thus no specific connections are indicated in themodification of the invention illustrated in FIGURE 2.

Additionally it will be noted that the spring 60 of the fuel meteringsystem illustrated in FIGURE 2 has been seated in chamber 48 rather thanin chamber 38. Thus it will be evident that it makes no difference inthe invention whether or not the pressure in the intermediate conduit 30is higher or lower than the pressure in the conduit 58. The onlydifference that changing the relative values of the pressures in theconduits 56 and 58 makes is that the ybias spring 60 must be changedbetween the chambers 38 and 40. The operation of the modification of thefuel metering system illustrated in FIGURE 2 is entirely analogous tothe operation of the fuel metering system illustrated in FIGURE l.

The modified fuel metering system illustrated in FIG- URE 3 differs fromthat of FIGURE 1 only in the provision of .the boost pump 62 and theplacing of the spring 60 in the chamber 4t) rather than in the chamber38. Thus the conduits 58 and 56 are connected into the transfer conduit28 and intermediate conduit 3i) as shown in FIG- URE 1. In thismodification it is assumed that the pressure drop across the combinedIfuel control package 14, consisting of the low pressure pump 16 and thefuel metering control 18 is a little greater than the pressure risecreated by pump 16. I-f spring 60 and diaphragm 42 were reversed asshown in FIGURE 4 the fuel metering system 10 would operate Iwith thepressure rise created by pump 16 greater than the pressure drop acrossthe con-trol package 14.

The modification of the fuel system 10 illustrated in FIGURE 4 furtherincludes a tank transfer pump 64 and a boost pump 62. It -will furtherbe noted that the chamber 38 in the modified fuel metering systemillustrated in FIGURE 4 is vented 4to the atmosphere rather thanconnected to the transfer conduit 28.

The modification of the metering system 10 which is shown in FIGURE 5 isidentical to the fuel metering system 10 except for the positioning ofthe spring 60 in the chamber 40 rather than in the chamber 38. Aspreviously indicated the position of the spring 611 may be changed dueto the pressure drop across the fuel metering control 14 being greaterthan the pressure increase across the low pressure pump 16.

The operation of the modification of the invention illustrated in FIGURE5 and the operation of the modification of the invention shown inFIGURES 3 and 4 is entirely analogous to the operation of the inventionillustrated in FIGURE 1.

In FIGURE 7 the pressure in discharge conduit 32 is shown plottedagainst fuel flow to an engine `for a rtypical installation of the fuelmetering system 10. Fuel flow in the installation represented in FIGURE7 Varies from a low of idle fuel ow to one hundred percent fuel flow asIthe pressure in discharge conduit 32 varies between 50 and 800 poundsper square inch. The fuel fiow to nozzle curve illustrated in FIGURE 7applies only if the nozzles are simplex, i.e., have a xed metering area.

In FIGURE 6 there is shown a modification 66 of the pressure sensitivevalve 22. The pressure sensitive valve 66 includes a main body portion68, an upper cap '70 and a plug 72. The body 68 and upper cap 70 includea diaphragm 74 therebetween whereby separate chambers 76 and 78 areprovided. The chamber 78 is connected directly to the conduit 58 asshown in FIGURE l, while the chamber 76 is connected to the low pressurereturn lconduit 56 through passage 80 and chamber 82. A valve 84 isslidably received in the passage 87 between the chambers 78 and 82 andis in engagement with the diaphragm 74 ywhich is biased toward the valve84 by means of the spring 86. The plug 72 and the body 68 form a chamber88 therebetween which is also in Comunication with the low pressurereturn conduit 56 through passage `9) and chamber 82. Body member 68further includes the chamber 92 formed therein which is in communicationwith the high pressure fuel return conduit 54, as shown in FIGURE l,through the passage 94. A passage 96 is provided between the chambers 88and 92 while an orifice 98 is provided between the chambers 92 and 82.The connector or pusher 100 is slidably positioned in the passage 96 andis biased into engagement with .the valve member 84 by means of thespring 102 as shown best in FIGURE 6. If desired the diameter of valvemember 84 may be such as to permit the valve member 84 to slide throughthe orifice 93 in which case fuel metering would be edge to edgemetering instead of the present edge to surface metering,

The operation of the pressure sensitive valve 66, as shown in FIGURE 6,is similar to that of the pressure sensitive valve 22 shown in FIGURES1-5. Thus the amount of fluid returned to conduit 56 from conduit 54 iscontrolled by the position of the valve member 84. The position of thevalve member 84 is under the direct control of the pressure differencein the chambers 76 and 78 as before. The springs 86 and 102 offer adifferential bias for the valve member 84 which is equal to thedifference in forces of springs 86 and 102 and is not compromised by thegeneral level of force in the springs. The rate of the springs 86 and182 is not particularly important as will be understood by those in theart. However, the load on the springs is different by the difference inpressure in lthe chambers 76 and 78 acting on the diaphragm 74.

The valve structure illustrated in FIGURE 6 has an added feature in thatit may also function as a relief valve. That is to say that whenpressure in chamber 92 exceed a predetermined value for a particularvalve area and force of spring 86 the valve 84 is forced upwardlyVinopposition to the bias of spring 86 to allow fluid to exit from chamber92 through orifice 98, chamber 82 and conduit 56. This additionalfunction of the valve 'structure 66 in no way compromises the majorfunction thereof `which is to make a slave control of the pump which isto say to cause the fiuid pumped to the nozzle 24 to be the same as thatmetered by the metering control 14.

While one embodiment of the present invention and some specificmodifications thereof have been disclosed in detail it will beunderstood that other embodiments and modifications of the invention arecontemplated. It is therefore the intention to include in the inventionall such modifications and embodiments of the invention as are definedby the appended claims.

What I claim as my invention is:

1. A fuel metering system for metering fuel to a utilizing device havingvarying fuel requirements comprising a source of fuel, a high pressurepositive displacement fuel pump operable at all times to pump a. massrate of fuel in excess of the total fuel requirements of the utilizingdevice having an output connected to the utilizing device, a fuelcontrol package connected between the source of fuel and the highpressure pump including a low pressure pump and a low pressure fuelmetering control for metering fuel to the high pressure pump from thesource of fuel in accordance with the requirements of the utilizingdevice and pressure responsive means connected across the fuel controlpackage for bypassing the quantity of fuel pumped by said high pressurepump in excess of the total fuel requirements of the utilizing deviceback to the input side of the high pressure pump so that the fuel fed tothe utilizing device from the high pressure pump is identical to thefuel metered to the input of the high pressure pump from the lowlpressure fuel metering control.

2. Structure as set forth in claim 1 wherein the pressure responsivemeans comprises a pressure sensitive valve including a housing, adiaphragm extending across and secured within said housing to form afirst and second chamber therein, means forming a third chamber in saidhousing, a valve orifice in said housing between the second and thirdchambers, a valve member engaging and movable with the diaphragm to varythe valve orifice and resilient valve biasing means operable between thehousing and diaphragm, means connecting the second chamber between thefuel metering control and high pressure pump and means connecting theoutput side of the high pressure pump to the third chamber.

3. Structure as set forth in claim 2 wherein the valve biasing means isa spring positioned within the second chamber and urging the valvemember in a direction to close the valve orifice between the second andthird chambers and further including a booster pump connected betweenthe source of fuel and the low pressure pump.

4. Structure as set forth in claim 1 wherein the pressure sensitivemeans comprises a valve including a house ing, a diaphragm securedwithin said housing forming a first and second chamber therewith, firstbias means Within the first of said chambers biasing the diaphragmtoward the second of said chambers, means forming third,

fourth and fifth chambers within said housing, a passage between thesecond and third chambers, a valve member engageable with said diaphragmand urged toward the third chamber slidably positioned within saidpassage, a

valve orifice between the third and fourth chambers, a

vpassage between the fourth and fth chambers, a pusher References Citedby the Examiner UNITED STATES PATENTS 1,768,904 7/1930 Harris137--505.43 2,292,574 S/1942 Laub 137-505.43 2,595,618 5/1952 Vogt etal.

2,633,187 3/1953 Smith 15S-36.3 2,679,206 5/1954 Huber 103-5 2,683,4187/1954 Smith.

2,730,167 1/1956 Sarto 15S-436.4 2,740,469 4/1956 Colestock 15S- 36.42,756,810 7/1956 Simmons 15S-36.4 3,003,520 10/1961 Corey 137-505.433,043,367 7/1962 Abraham 158--36.4 3,056,259 10/1962 Jubb et al15S-36.4-

FREDERICK L. MATTESON, IR., Primary Examiner.

FREDERICK KETTERER, JAMES W. WESTHAVER,

PERCY L. PATRICK, Examiners.

1. A FUEL METERING SYSTEM FOR METERING FUEL TO A UTILIZING DEVICE HAVINGVARYING FUEL REQUIREMENTS COMPRISING A SOURCE OF FUEL, A HIGH PRESSUREPOSITIVE DISPLACEMENT FUEL PUMP OPERABLE AT ALL TIMES TO PUMP A MASSRATE OF FUEL IN EXCESS OF THE TOTAL FUEL REQUIREMENTS OF THE UTILIZINGDEVICE HAVING AN OUTPUT CONNECTEDS TO THE UTILIZING DEVICE, A FUELCONTROL PACKAGE CONNECTED BETWEEN THE SOURCE OF FUEL AND THE HIGHPRESSURE PUMP INCLUDING A LOW PRESSURE PUMP AND A LOW PRESSURE FUELMETERING CONTROL FOR METERING FUEL TO THE HIGH PRESSURE PUMP FROM THESOURCE OF FUEL IN ACCORDANCE WITH THE REQUIREMENTS OF THE UTILIZINGDEVICE AND PRESSURE RESPONSIVE MEANS CONNECTED ACROSS THE FUEL CONTROLPACKAGE FOR BYPASSING THE QUANTITY OF FUEL PUMPED BY SAID HIGH PRESSUREPUMP IN EXCESS OF THE TOTAL FUEL REQUIREMENTS OF THE UTILIZING DEVICEBACK TO THE INPUT SIDE OF THE HIGH PRESSURE PUMP SO THAT THE FUEL FED TOTHE UTILIZING DEVICE FROM THE HIGH PRESSURE PUMP IS IDENTICAL TO THEFUEL METERED TO THE INPUT OF THE HIGH PRESSURE FROM THE LOW PRESSUREFUEL METERING CONTROL.